Primochill tubing and distilled water is not enough to prevent growth. You need anti-algae stuff (PT Nuke), or specific liquids (Feser, Primochill, Swiftech all sell some).

The problem is not using the holes, but bending the tubing from the hole to the rad barb - this is a severe bend, and will probably result in a kink of the tube. You will need special 90* and 45* swivel barbs.

If you wish to drill holes up top a la P180 (my first pic), then you need a power drill with a step bit, and grommets to cover the hole edges. It can be done.